Add tetris example

tetris/block.py

@@ -0,0 +1,10 @@
+class Block:
+    """A Block represents a single square on the Tetris board. 
+    Blocks are part of a Piece while they are 'alive'.
+    """
+    character = "X"
+    color = "blue"
+    alive = True
+
+    def __init__(self, position):
+        self.position = position